Ferric iron and extracellular electron shuttling increase xylose utilization and butanol production during fermentation with multiple solventogenic bacteria

Jovan Popovic, Xiaofeng Ye, Anne Haluska, Kevin T. Finneran

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Xylose is the second most abundant sugar derived from lignocellulose; it is considered less desirable than glucose for fermentation, and strategies that specifically increase xylose utilization in wild-type cells are goals for biofuel production. Xylose consumption, butanol production, and hydrogen production increased in both Clostridium beijerinckii and a novel solventogenic bacterium (strain DC-1) when anthraquinone-2,6,-disulfonate (AQDS) or riboflavin were used as redox mediators to transfer electrons to poorly crystalline Fe(OH)3 as an extracellular electron sink. Strain DC-1 was most closely related to Rhizobiales bacterium Mfc52 based on 95% 16S rRNA gene sequence similarity, which demonstrates that this response is not limited to a single genus of xylose-fermenting bacteria. Xylose utilization and butanol production were negligible in control incubations containing cells plus 3% (w/v) xylose alone during a 10-day batch fermentation, for both strains tested (n-butanol titers of 0.05 g L−1). Micromolar concentrations of AQDS and riboflavin were added as electron shuttling compounds with poorly crystalline Fe(OH)3 as an insoluble electron acceptor, and respective n-butanol titers increased to 6.35 and 7.46 g L−1. Increases in xylose consumption for the iron treatments were relatively high, from less than 0.49 g L−1 (xylose alone, no iron or electron shuttling molecules) to 25.98 and 29.15 g L−1 for the AQDS and riboflavin treatments, respectively. Hydrogen production was also 3.68 times greater for the AQDS treatment and 5.27 greater for the riboflavin treatment relative to controls. Strain DC-1 data were similar, again indicating that the effects are not specific to the genus Clostridium.

Original languageEnglish (US)
Pages (from-to)8053-8061
Number of pages9
JournalApplied Microbiology and Biotechnology
Volume101
Issue number21
DOIs
StatePublished - Nov 1 2017

Bibliographical note

Funding Information:
Funding information This work was partially funded by the National Science Foundation (grant number 0756054).

Keywords

  • Bio butanol
  • Biofuels
  • Electron shuttling
  • Iron reduction
  • Xylose fermentation

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